Envirowave Energy provides a solution to the effective treatment
of organic materials processed by municipal sewage plants, in
a cost-effective manner. The EnviroWave process employs a combination
of microwave and hot gas convection technologies to achieve these
goals. This concept provides the most cost effective solution
while achieving the total destruction of pathogens, resulting
in a biosolid product which may be directly land-applied as an
EPA-certified, Class A material.

Current treatment methods primarily expose municipal waste
(biosolids) to a high pH-high temperature process to reduce pathogens,
but do not necessarily achieve a Class A product. A solution
must include (1) pathogen reduction to achieve a Class A product
under U.S. Regulations, 40 CFR, Part 503, Alternative 6, (2)
odor reduction and (3) economic viability.

Test results by an independent laboratory recommended by the
U.S. EPA have confirmed the Envirowave microwave apparatus achieves
total and complete destruction of all pathogens, without adhering
to the previous requirement of time and temperature profiles.
In addition, the dryness requirement is actually considerably
less than previous EPA requirements. This contributes to less
energy consumption, which further improves the economic factors.

Microwave Generator Design

The microwave generator serves as the source of microwaves
for the applicator. To promote stability of operation for the
microwave generator, and ultimately the microwave applicator,
the power supply must be stable, as well as free of ripple voltage
and harmonics on the output waveforms. Stability, noise-free
outputs and power factor improvement are achieved by the EnviroWave
system design.

Cooling water is provided to the magnetron from a reservoir
of de-mineralized water. Cooling air is provided to the magnetron
stem and dome by two separate radial fans.

Specific waveguide launcher design details are defined by
the magnetron manufacturer and chosen for optimum magnetron performance.
Optimum performance usually results in a compromise of efficiency,
power output and stability when operating with mismatched loads.
A programmable, stand alone, Programmable Logic Controller (PLC)
controls each generator during startup, operation and shutdown.
The PLC Program is designed to automatically start/stop the generators,
automatically start/stop the applicator and automatically load/unload
the generators to pre-defined operating points via the ramp up/down
schedule.

For maximum protection of personnel and equipment, all shutdowns
and emergency stop buttons are hardwired in series, external
to the PLC program, for immediate, manual emergency shutdown,
of all operating systems.

Microwave Applicator Design

Volumetric Heating is defined as the fixed continuous power
dissipation by a volume of dielectric material, causing the average
temperature of the material to rise linearly with time, as long
as the power is applied, without consideration to the temperature
of the applicator walls or air within the applicator.

Obviously, the effects of temperature, specific heat, humidity
and circulating airflow within the applicator do contribute to
changes in the surface temperature of the material, due to heat
transfer characteristics of the surface material. The changes
in the surface material of the dielectric load results in overall
secondary heating or cooling effects. As the material is conveyed
through the applicator, changes which occur in the material size/shape,
temperature and moisture content directly affect the microwave
absorption characteristics.

The separation and definition of material size and shape,
directly affects hot gas flow between the particles of material
on the belt, resulting in a changing a rate of evaporation. In
bio-solids, the presence of lime and polymer contributes to changes
in both microwave absorption and hot gas flow between the particles.

Microwave drying rapidly drives the moisture from inside the
material to the surfaces of the material. Temperature gradients
can form at the surface of the material due to the difference
in internal and surface temperatures. At temperatures below the
boiling point of water, the temperature differential assists
in driving the moisture to the material surface. Through capillary
action within the pores of the material, the microwave absorption
and resulting temperature differential forces the water toward
the material surfaces.

The design incorporates improved convection air movement,
which subsequently increased material surface moisture evaporation
rates, as well as reducing the rate of gas consumption. The higher
velocity, hot-convection air moving parallel to the material
flow, but opposite in direction, results in a higher rate of
removal of surface moisture from the material.

The hot gas convection section of the combined microwave/convection
applicator consists of burners, circulating fans, an insulated
air plenum, and an exhaust blower. The convection air is drawn
from the burners, across the applicator width (top) into radial
inflow blowers, down an insulated plenum chamber covering the
entire applicator length (side), where it is eventually drawn
out, along with moisture-laden air through an exhaust blower.

For more information about the Envirowave Energy and commercial
microwave technology please click on the Contact
Us link on the top right of the web page.